The detection and study of corrosion of small metal and insulator structures is important economically in the processing and reliability of semiconductors and similar devices. The use of fluorescent compounds for such use, as a general matter, is known. U.S. Pat. No. 4,039,838, for example, discloses the use of an amorphous coating of a fluorescent compound on a substrate transparent to visible light to examine photomasks by ultraviolet light.
U.S. Pat. No. 3,530,045 discloses the use of layers of stiff gel containing a color indicator and a conductive liquid to detect defects in conductive test parts. In this method, the color indicator gel is interposed between the test piece and the conductive liquid-containing gel, which function as oppositely charged electrodes when an electrical current is passed therethrough.
U.S. Pat. No. 4,278,508 discloses the use of a pH sensitive fluorescent compound to detect a cathodic corrosion site in a metallic surface of the substrate. The dye is coated on the metallic surface and an electrical bias is applied thereto. The surface is then exposed to ultraviolet light whereupon the corrosion sites fluoresce. U.S. Pat. No. 4,237,379 discloses a means of testing the quality of a protective layer in devices, such as integrated circuit devices, by applying a fluorescein-containing compound thereto and exposing to UV irradiation while applying a voltage between two conductors.
Improvements in the use of fluroescent compounds to detect microdefects in the surface layer of, e.g., semiconductor devices, are provided in accordance with this invention.